Diagnostic performance of fluorodeoxyglucose-positron emission tomography/computed tomography combined with ultrasonography-guided fine needle aspiration cytology for identifying axillary lymph node status in patients with breast cancer

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Abstract

Aim

The aim of this study was to assess the diagnostic performance of fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) in combination with ultrasonography-guided fine needle aspiration cytology (US-guided FNAC) for the preoperative diagnosis of axillary lymph node (ALN) metastases in patients with breast cancer.

Materials and methods

A total of 318 patients with breast cancer were recruited retrospectively. Some of the cases that underwent neoadjuvant chemotherapy (NAC) were included. The sensitivity and specificity of FDG-PET/CT were calculated. We assessed the relationship between the combined results for US-guided FNAC with FDG-PET/CT and the pathological ALN status.

Results

A total of 271 patients underwent FDG-PET/CT. Of these patients, 41 underwent US-guided FNAC. The sensitivity and the specificity of FDG-PET/CT for the cases without NAC were 18.5%, 97.1%, respectively. The sensitivity in cases with NAC was 68.2%. As a whole, the sensitivity was 40.8%.

ALN metastasis was detected using US-guided FNAC in a case with a negative FDG uptake in the ALN. The T stage was T2 in the case and the FDG uptake at the primary site was poor.

Conclusion

FDG-PET/CT has a good specificity for ALN metastasis, although its sensitivity is limited, especially in early-stage cases. In cases with a negative FDG uptake in the ALN, US-guided FNAC may play a role in the detection of lymph node metastasis when the primary tumor size is large and the FDG uptake in the primary tumor is low.

Introduction

The axillary lymph node (ALN) status is one of the most important prognostic factors in newly diagnosed breast cancer patients.1 The preoperative recognition of ALN positivity is important for deciding on the surgical approach for the ALN.2, 3, 4

Preoperative lymph node staging has been introduced using various modalities including ultrasonography (US), computed tomography, magnetic resonance imaging, and positron emission tomography.5, 6, 7 Positron emission tomography with 18F-fluorodeoxyglucose (FDG-PET) has been used for the diagnosis and management of breast cancer.5 Although several early studies on FDG-PET for axillary staging showed both high sensitivities and specificities, low sensitivities for PET have been reported in most studies, especially in patients with small primary tumors.5, 8

Ultrasonography (US) is widely performed for the preoperative diagnosis of breast cancer. US in combination with US-guided percutaneous fine needle aspiration cytology (US-guided FNAC) has also provided accurate results for determining the ALN status, providing a moderate sensitivity and a high specificity for the preoperative assessment of ALN.2, 9, 10, 11

Although a few studies have reported the use of FDG-PET or FDG-PET/CT in combination with US for axillary staging in primary breast cancer,12, 13 studies evaluating FDG-PET/CT in combination with US-guided FNAC for preoperative axillary staging have not been described. The aim of the present study was to assess the diagnostic performance of FDG-PET/CT in combination with US-guided FNAC for the preoperative diagnosis of ALN metastases of breast cancer.

Section snippets

Patients

The study protocol was approved by the local ethics committee. Patients who underwent surgery for breast cancer between December 2005 and November 2009 at our institution were reviewed retrospectively. During the study period, 318 cases with breast cancer underwent preoperative FDG-PET/CT. Some of these patients had undergone neoadjuvant chemotherapy (NAC) prior to axillary surgery. Patients, whose initial ALN statuses were unclear, because of the effect of NAC, were excluded from the present

Patient characteristics

Of the 318 cases, 227 underwent surgery without NAC and the other 91 cases underwent NAC prior to surgery. Among the cases with NAC, ALN metastases were identified by FNAC prior to NAC in 13 cases and based on the histopathological analysis in 31 cases. These cases were included in the present study. The remaining 47 cases with NAC were excluded from the analysis because their initial ALN statuses were unknown. A total of 271 cases, 227 without NAC and 44 with NAC, were enrolled in the present

Performance of FDG-PET/CT

The specificity of PET for axillary staging has been consistently high in previous reports, ranging from 75% to 100%.5 In the present study, the specificity of FDG-PET/CT among the cases without NAC was also high. On the other hand, the sensitivity was 40.8% overall, indicating that more than half of all patients with ALN metastases are overlooked. The sensitivity of FDG-PET/CT decreased to 18.5% for the cases without NAC, probably because the cases without NAC had an early stage than those

Conclusion

In conclusion, FDG-PET/CT has a good specificity for ALN metastasis, although its sensitivity is limited, especially in early-stage cases. In cases with a negative FDG uptake in the ALN, US-guided FNAC may play a role in the detection of lymph node metastasis when the primary tumor size is large and FDG uptake in the primary tumor is low.

Conflict of interest

The authors declare that there are no conflicts of interest.

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